Just a remote possability, Last summer I was on a 400 mile trip, pulled into a forcourt for fuel when the dreadded '35 mph' came up on the dash, I knew the suspension was ok, so I stopped & started pushing all the dash buttons, pressed the diff-lock, heard it 'click in', pressed it again, heard it 'click out' & the speed message went out !! Its never done it since. computer glitch??